Double one-dimensional sector sweep scan

ABSTRACT

Certain aspects of the present disclosure provide methods and apparatus for enhancing a sector sweep. The apparatus generally includes a processing system configured to generate a first set of frames and a second set of frames. The apparatus also includes a first interface configured to output the first set of frames for transmission to a wireless node via a first set of beams, wherein each beam of the first set is wider in a first dimension than a second dimension, and output the second set of frames for transmission to the wireless node via a second set of beams, wherein each beam of the second set is wider in the second dimension than the first dimension.

CLAIM OF PRIORITY UNDER 35 U.S.C. § 119

This application is a divisional application of U.S. Non-Provisionalapplication Ser. No. 16/294,141, filed Mar. 6, 2019, which claimspriority to U.S. Provisional Application No. 62/646,792, filed Mar. 22,2018, both of which are assigned to the assignee of the presentapplication and hereby expressly incorporated by reference herein intheir entireties.

FIELD

Certain aspects of the present disclosure generally relate to wirelesscommunications and, more particularly, systems and methods for improvinga sector sweep using a one-dimensional sector sweep.

BACKGROUND

In order to address the issue of increasing bandwidth requirementsdemanded for wireless communications systems, different schemes arebeing developed to allow multiple user terminals to communicate with asingle access point by sharing the channel resources while achievinghigh data throughputs.

Certain wireless communications standards, such as the Institute ofElectrical and Electronics Engineers (IEEE) 802.11 standard, denotes aset of Wireless Local Area Network (WLAN) air interface standardsdeveloped by the IEEE 802.11 committee for short-range communications(e.g., tens of meters to a few hundred meters).

Amendments 802.11ad, 802.11ay, and 802.11az to the WLAN standard definethe MAC and PHY layers for very high throughput (VHT) in the 60 GHzrange. Operations in the 60 GHz band allow the use of smaller antennasas compared to lower frequencies. However, as compared to operating inlower frequencies, radio waves around the 60 GHz band have highatmospheric attenuation and are subject to higher levels of absorptionby atmospheric gases, rain, objects, and the like, resulting in higherfree space loss. The higher free space loss can be compensated for byusing many small antennas, for example arranged in a phased array.

Using a phased array, multiple antennas may be coordinated to form acoherent beam traveling in a desired direction (or beam), referred to asbeamforming (BF). An electrical field may be rotated to change thisdirection. The resulting transmission is polarized based on theelectrical field. A receiver may also include antennas which can adaptto match or adapt to changing transmission polarity.

SUMMARY

The systems, methods, and devices of the disclosure each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this disclosure as expressedby the claims which follow, some features will now be discussed briefly.After considering this discussion, and particularly after reading thesection entitled “Detailed Description” one will understand how thefeatures of this disclosure provide advantages that include improvedcommunications between access points and stations in a wireless network.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes a processingsystem configured to generate a first set of frames and a second set offrames. The apparatus also includes a first interface configured tooutput the first set of frames for transmission to a wireless node via afirst set of beams, wherein each beam of the first set is wider in afirst dimension than a second dimension, and output the second set offrames for transmission to the wireless node via a second set of beams,wherein each beam of the second set is wider in the second dimensionthan the first dimension.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes a firstinterface configured to obtain, from a wireless node, a first set offrames transmitted via a first set of beams, wherein each beam of thefirst set is wider in a first dimension than a second dimension, and asecond set of frames transmitted via a second set of beams, wherein eachbeam of the second set is wider in the second dimension than the firstdimension. The apparatus also includes a processing system configured tolog reception parameters for the first and second sets of frames and todetermine at least one of an angle of departure of the first and secondsets of frames, a location of the apparatus relative to the wirelessnode, or an absolute location of the apparatus.

Aspects of the present disclosure also provide various methods, means,and computer program products corresponding to the apparatuses andoperations described above.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed, and this description is intended to include all suchaspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description,briefly summarized above, may be had by reference to aspects, some ofwhich are illustrated in the appended drawings. It is to be noted,however, that the appended drawings illustrate only certain typicalaspects of this disclosure and are therefore not to be consideredlimiting of its scope, for the description may admit to other equallyeffective aspects.

FIG. 1 is a diagram of an example wireless communications network, inaccordance with certain aspects of the present disclosure.

FIG. 2 is a block diagram of an example access point and example userterminals, in accordance with certain aspects of the present disclosure.

FIG. 3 is a diagram illustrating signal propagation in an implementationof phased-array antennas, in accordance with certain aspects of thepresent disclosure.

FIG. 4 illustrates an example beamforming training procedure, inaccordance with certain aspects of the present disclosure.

FIG. 5 illustrates an example radiation pattern of “pencil” beams, inaccordance with certain aspects of the present disclosure.

FIG. 6 illustrates example operations for performing a one-dimensionalsector sweep by a sweep initiator, in accordance with certain aspects ofthe present disclosure.

FIG. 6A illustrates example components capable of performing theoperations shown in FIG. 6, in accordance with certain aspects of thepresent disclosure.

FIG. 7 illustrates example operations for performing a one-dimensionalsector sweep by a sweep receiver, in accordance with certain aspects ofthe present disclosure.

FIG. 7A illustrates example components capable of performing theoperations shown in FIG. 7, in accordance with certain aspects of thepresent disclosure.

FIG. 8 illustrates an example radiation pattern of elevation beams, inaccordance with certain aspects of the present disclosure.

FIG. 9 illustrates an example radiation pattern of azimuthal beams, inaccordance with certain aspects of the present disclosure.

FIG. 10 illustrates an example wireless system for determiningpositioning, in accordance with certain aspects of the presentdisclosure.

DETAILED DESCRIPTION

Certain aspects of the present disclosure provide methods and apparatusfor enhancing a sector sweep using a one-dimensional sector sweep asfurther described herein.

Various aspects of the disclosure are described more fully hereinafterwith reference to the accompanying drawings. This disclosure may,however, be embodied in many different forms and should not be construedas limited to any specific structure or function presented throughoutthis disclosure. Rather, these aspects are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of the disclosure to those skilled in the art. Based on theteachings herein one skilled in the art should appreciate that the scopeof the disclosure is intended to cover any aspect of the disclosuredisclosed herein, whether implemented independently of or combined withany other aspect of the disclosure. For example, an apparatus may beimplemented or a method may be practiced using any number of the aspectsset forth herein. In addition, the scope of the disclosure is intendedto cover such an apparatus or method which is practiced using otherstructure, functionality, or structure and functionality in addition toor other than the various aspects of the disclosure set forth herein. Itshould be understood that any aspect of the disclosure disclosed hereinmay be embodied by one or more elements of a claim.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any aspect described herein as “exemplary”is not necessarily to be construed as preferred or advantageous overother aspects.

Although particular aspects are described herein, many variations andpermutations of these aspects fall within the scope of the disclosure.Although some benefits and advantages of the preferred aspects arementioned, the scope of the disclosure is not intended to be limited toparticular benefits, uses, or objectives. Rather, aspects of thedisclosure are intended to be broadly applicable to different wirelesstechnologies, system configurations, networks, and transmissionprotocols, some of which are illustrated by way of example in thefigures and in the following description of the preferred aspects. Thedetailed description and drawings are merely illustrative of thedisclosure rather than limiting, the scope of the disclosure beingdefined by the appended claims and equivalents thereof.

Example Wireless Communication System

The techniques described herein may be used for various broadbandwireless communication systems, including communication systems that arebased on an orthogonal multiplexing scheme. Examples of suchcommunication systems include Spatial Division Multiple Access (SDMA),Time Division Multiple Access (TDMA), Orthogonal Frequency DivisionMultiple Access (OFDMA) systems, Single-Carrier Frequency DivisionMultiple Access (SC-FDMA) systems, and so forth. An SDMA system mayutilize sufficiently different directions to simultaneously transmitdata belonging to multiple user terminals. A TDMA system may allowmultiple user terminals to share the same frequency channel by dividingthe transmission signal into different time slots, each time slot beingassigned to different user terminal. An OFDMA system utilizes orthogonalfrequency division multiplexing (OFDM), which is a modulation techniquethat partitions the overall system bandwidth into multiple orthogonalsub-carriers. These sub-carriers may also be called tones, bins, etc.With OFDM, each sub-carrier may be independently modulated with data. AnSC-FDMA system may utilize interleaved FDMA (IFDMA) to transmit onsub-carriers that are distributed across the system bandwidth, localizedFDMA (LFDMA) to transmit on a block of adjacent sub-carriers, orenhanced FDMA (EFDMA) to transmit on multiple blocks of adjacentsub-carriers. In general, modulation symbols are sent in the frequencydomain with OFDM and in the time domain with SC-FDMA. The techniquesdescribed herein may be utilized in any type of applied to SingleCarrier (SC) and SC-MIMO systems.

The teachings herein may be incorporated into (e.g., implemented withinor performed by) a variety of wired or wireless apparatuses (e.g.,nodes). In some aspects, a wireless node implemented in accordance withthe teachings herein may comprise an access point or an access terminal.

An access point (“AP”) may comprise, be implemented as, or known as aNode B, a Radio Network Controller (“RNC”), an evolved Node B (eNB), aBase Station Controller (“BSC”), a Base Transceiver Station (“BTS”), aBase Station (“BS”), a Transceiver Function (“TF”), a Radio Router, aRadio Transceiver, a Basic Service Set (“BSS”), an Extended Service Set(“ES S”), a Radio Base Station (“RBS”), or some other terminology.

An access terminal (“AT”) may comprise, be implemented as, or known as asubscriber station, a subscriber unit, a mobile station, a remotestation, a remote terminal, a user terminal, a user agent, a userdevice, user equipment, a user station, or some other terminology. Insome implementations, an access terminal may comprise a cellulartelephone, a cordless telephone, a Session Initiation Protocol (“SIP”)phone, a wireless local loop (“WLL”) station, a personal digitalassistant (“PDA”), a handheld device having wireless connectioncapability, a Station (“STA”), or some other suitable processing deviceconnected to a wireless modem. Accordingly, one or more aspects taughtherein may be incorporated into a phone (e.g., a cellular phone or smartphone), a computer (e.g., a laptop), a portable communication device, aportable computing device (e.g., a personal data assistant), anentertainment device (e.g., a music or video device, or a satelliteradio), a global positioning system device, or any other suitable devicethat is configured to communicate via a wireless or wired medium. Insome aspects, the node is a wireless node. Such wireless node mayprovide, for example, connectivity for or to a network (e.g., a widearea network such as the Internet or a cellular network) via a wired orwireless communication link.

FIG. 1 illustrates a multiple-access multiple-input multiple-output(MIMO) system 100 with access points and user terminals. Certain aspectsof the present disclosure generally relate to improving a sector sweepusing a one-dimensional sector sweep. For example, the scanning time toperform a sweep may be reduced using a one-dimensional sector sweepbetween access points and/or user terminals as further described hereinwith respect to FIGS. 6-10.

For simplicity, only one access point 110 is shown in FIG. 1. An accesspoint is generally a fixed station that communicates with the userterminals and may also be referred to as a base station or some otherterminology. A user terminal may be fixed or mobile and may also bereferred to as a mobile station, a wireless device or some otherterminology. Access point 110 may communicate with one or more userterminals 120 at any given moment on the downlink and uplink. Thedownlink (i.e., forward link) is the communication link from the accesspoint to the user terminals, and the uplink (i.e., reverse link) is thecommunication link from the user terminals to the access point. A userterminal may also communicate peer-to-peer with another user terminal. Asystem controller 130 couples to and provides coordination and controlfor the access points.

While portions of the following disclosure will describe user terminals120 capable of communicating via Spatial Division Multiple Access(SDMA), for certain aspects, the user terminals 120 may also includesome user terminals that do not support SDMA. Thus, for such aspects, anaccess point (AP) 110 may be configured to communicate with both SDMAand non-SDMA user terminals. This approach may conveniently allow olderversions of user terminals (“legacy” stations) to remain deployed in anenterprise, extending their useful lifetime, while allowing newer SDMAuser terminals to be introduced as deemed appropriate.

The system 100 employs multiple transmit and multiple receive antennasfor data transmission on the downlink and uplink. The access point 110is equipped with N_(ap) antennas and represents the multiple-input (MI)for downlink transmissions and the multiple-output (MO) for uplinktransmissions. A set of K selected user terminals 120 collectivelyrepresents the multiple-output for downlink transmissions and themultiple-input for uplink transmissions. For pure SDMA, it is desired tohave N_(ap)≥K≥1 if the data symbol streams for the K user terminals arenot multiplexed in code, frequency or time by some means. K may begreater than N_(ap) if the data symbol streams can be multiplexed usingTDMA technique, different code channels with CDMA, disjoint sets ofsubbands with OFDM, and so on. Each selected user terminal transmitsuser-specific data to and/or receives user-specific data from the accesspoint. In general, each selected user terminal may be equipped with oneor multiple antennas (i.e., N_(ut)≥1). The K selected user terminals canhave the same or different number of antennas.

The system 100 may be a time division duplex (TDD) system or a frequencydivision duplex (FDD) system. For a TDD system, the downlink and uplinkshare the same frequency band. For an FDD system, the downlink anduplink use different frequency bands. MIMO system 100 may also utilize asingle carrier or multiple carriers for transmission. Each user terminalmay be equipped with a single antenna (e.g., in order to keep costsdown) or multiple antennas (e.g., where the additional cost can besupported). The system 100 may also be a TDMA system if the userterminals 120 share the same frequency channel by dividingtransmission/reception into different time slots, each time slot beingassigned to different user terminal 120.

FIG. 2 illustrates a block diagram of access point 110 and two userterminals 120 m and 120 x in MIMO system 100. In certain aspects, theaccess point 110 and/or the user terminals 120 m and 120 x may performone-dimensional sector sweep scans, for example, to perform beamformingtraining as further described herein with respect to FIGS. 6-10.

The access point 110 is equipped with N_(t) antennas 224 a through 224t. User terminal 120 m is equipped with N_(ut,m) antennas 252 ma through252 mu, and user terminal 120 x is equipped with N_(ut,x) antennas 252xa through 252 xu. The access point 110 is a transmitting entity for thedownlink and a receiving entity for the uplink. Each user terminal 120is a transmitting entity for the uplink and a receiving entity for thedownlink. As used herein, a “transmitting entity” is an independentlyoperated apparatus or device capable of transmitting data via a wirelesschannel, and a “receiving entity” is an independently operated apparatusor device capable of receiving data via a wireless channel. The termcommunication generally refers to transmitting, receiving, or both. Inthe following description, the subscript “dn” denotes the downlink, thesubscript “up” denotes the uplink, Nup user terminals are selected forsimultaneous transmission on the uplink, Ndn user terminals are selectedfor simultaneous transmission on the downlink, Nup may or may not beequal to Ndn, and Nup and Ndn may be static values or can change foreach scheduling interval. The beam-steering or some other spatialprocessing technique may be used at the access point and user terminal.

On the uplink, at each user terminal 120 selected for uplinktransmission, a TX data processor 288 receives traffic data from a datasource 286 and control data from a controller 280. TX data processor 288processes (e.g., encodes, interleaves, and modulates) the traffic datafor the user terminal based on the coding and modulation schemesassociated with the rate selected for the user terminal and provides adata symbol stream. A TX spatial processor 290 performs spatialprocessing on the data symbol stream and provides N_(ut,m) transmitsymbol streams for the N_(ut,m) antennas. Each transmitter unit (TMTR)254 receives and processes (e.g., converts to analog, amplifies,filters, and frequency upconverts) a respective transmit symbol streamto generate an uplink signal. N_(ut,m) transmitter units 254 provideN_(ut,m) uplink signals for transmission from N_(ut,m) antennas 252 tothe access point.

Nup user terminals may be scheduled for simultaneous transmission on theuplink. Each of these user terminals performs spatial processing on itsdata symbol stream and transmits its set of transmit symbol streams onthe uplink to the access point.

At access point 110, N_(ap) antennas 224 a through 224 ap receive theuplink signals from all Nup user terminals transmitting on the uplink.Each antenna 224 provides a received signal to a respective receiverunit (RCVR) 222. Each receiver unit 222 performs processingcomplementary to that performed by transmitter unit 254 and provides areceived symbol stream. An RX spatial processor 240 performs receiverspatial processing on the N_(ap) received symbol streams from N_(ap)receiver units 222 and provides Nup recovered uplink data symbolstreams. The receiver spatial processing is performed in accordance withthe channel correlation matrix inversion (CCMI), minimum mean squareerror (MMSE), soft interference cancellation (SIC), or some othertechnique. Each recovered uplink data symbol stream is an estimate of adata symbol stream transmitted by a respective user terminal. An RX dataprocessor 242 processes (e.g., demodulates, deinterleaves, and decodes)each recovered uplink data symbol stream in accordance with the rateused for that stream to obtain decoded data. The decoded data for eachuser terminal may be provided to a data sink 244 for storage and/or acontroller 230 for further processing.

On the downlink, at access point 110, a TX data processor 210 receivestraffic data from a data source 208 for Ndn user terminals scheduled fordownlink transmission, control data from a controller 230, and possiblyother data from a scheduler 234. The various types of data may be senton different transport channels. TX data processor 210 processes (e.g.,encodes, interleaves, and modulates) the traffic data for each userterminal based on the rate selected for that user terminal. TX dataprocessor 210 provides Ndn downlink data symbol streams for the Ndn userterminals. A TX spatial processor 220 performs spatial processing (suchas a precoding or beamforming, as described in the present disclosure)on the Ndn downlink data symbol streams, and provides N_(ap) transmitsymbol streams for the N_(ap) antennas. Each transmitter unit 222receives and processes a respective transmit symbol stream to generate adownlink signal. N_(ap) transmitter units 222 providing N_(ap) downlinksignals for transmission from N_(ap) antennas 224 to the user terminals.

At each user terminal 120, N_(ut,m) antennas 252 receive the N_(ap)downlink signals from access point 110. Each receiver unit 254 processesa received signal from an associated antenna 252 and provides a receivedsymbol stream. An RX spatial processor 260 performs receiver spatialprocessing on N_(ut,m) received symbol streams from N_(ut,m) receiverunits 254 and provides a recovered downlink data symbol stream for theuser terminal. The receiver spatial processing is performed inaccordance with the CCMI, MMSE or some other technique. An RX dataprocessor 270 processes (e.g., demodulates, deinterleaves and decodes)the recovered downlink data symbol stream to obtain decoded data for theuser terminal.

At each user terminal 120, a channel estimator 278 estimates thedownlink channel response and provides downlink channel estimates, whichmay include channel gain estimates, SNR estimates, noise variance and soon. Similarly, a channel estimator 228 estimates the uplink channelresponse and provides uplink channel estimates. Controller 280 for eachuser terminal typically derives the spatial filter matrix for the userterminal based on the downlink channel response matrix H_(dn,m) for thatuser terminal. Controller 230 derives the spatial filter matrix for theaccess point based on the effective uplink channel response matrixH_(up,eff). Controller 280 for each user terminal may send feedbackinformation (e.g., the downlink and/or uplink eigenvectors, eigenvalues,SNR estimates, and so on) to the access point. Controllers 230 and 280also control the operation of various processing units at access point110 and user terminal 120, respectively.

Certain standards, such as the IEEE 802.11ay standard, extend wirelesscommunications according to existing standards (e.g., the 802.11adstandard) into the 60 GHz band. Example features to be included in suchstandards include channel aggregation and Channel-Bonding (CB). Ingeneral, channel aggregation utilizes multiple channels that are keptseparate, while channel bonding treats the bandwidth of multiplechannels as a single (wideband) channel.

As described above, operations in the 60 GHz band may allow the use ofsmaller antennas as compared to lower frequencies. While radio wavesaround the 60 GHz band have relatively high atmospheric attenuation, thehigher free space loss can be compensated for by using many smallantennas, for example arranged in a phased array.

Using a phased array, multiple antennas may be coordinated to form acoherent beam traveling in a desired direction. An electrical field maybe rotated to change this direction. The resulting transmission ispolarized based on the electrical field. A receiver may also includeantennas which can adapt to match or adapt to changing transmissionpolarity.

FIG. 3 is a diagram illustrating signal propagation 300 in animplementation of phased-array antennas. Phased array antennas useidentical elements 310-1 through 310-4 (hereinafter referred toindividually as an element 310 or collectively as elements 310). Thedirection in which the signal is propagated yields approximatelyidentical gain for each element 310, while the phases of the elements310 are different. Signals received by the elements are combined into acoherent beam with the correct gain in the desired direction.

In high frequency (e.g., mmWave) communication systems like 60 GHz(e.g., 802.11ad, 802.11ay, and 802.11az), communication is based onbeamforming (BF), using phased arrays on both sides for achieving goodlink. As described above, beamforming (BF) generally refers to amechanism used by a pair of STAs to adjust transmit and/or receiveantenna settings achieve desired link budget for subsequentcommunication. As will be described in greater detail below, in somecases, a one-dimensional sector may be formed using beamforming.

As illustrated in FIG. 4, BF training typically involves a bidirectionalsequence of BF training frame transmissions between stations (STA1 andSTA2 in this example) that uses a sector sweep followed by a beamrefining phase (BRP). For example, an AP or non-AP STA may initiate sucha procedure to establish an initial link. During the sector sweep, eachtransmission is sent using a different sector (covering a directionalbeam of a certain width) identified in the frame and provides thenecessary signaling to allow each STA to determine appropriate antennasystem settings for both transmission and reception.

As illustrated in FIG. 4, in all cases where the AP has large number ofelements, the sectors used are relatively narrow, causing the SLS(Sector Level Sweep) process to be long. The higher the directivity moresectors are needed and therefore the SLS is longer. As an example, an APwith an array of 100 antenna elements may use 100 sectors. Thissituation is not desired since SLS is an overhead, which affectsthroughput, power consumption, and induces a gap in the transport flow.Thus, the SLS contributes to latency and power consumption.

Various techniques may be used to try and reduce the SLS duration. Forexample, each Sector Sweep (SSW) frame may have a duration of about 15microseconds and transmitted via a pencil beam 502 as illustrated inFIG. 5, which depicts an example radiation pattern of pencil beams 504,in accordance with certain aspects of the present disclosure. With atransmitter having 256 pencil beam sectors (of which only 25 are shownin FIG. 5), the sector sweep may take about 3.8 milliseconds. A shorterSSW (SSSW) message (e.g., 9.6 microseconds) may be used, which may savesome time (e.g., about 36%), but this still results in the256-pencil-beam example taking about 2.5 milliseconds to complete thesector sweep.

In some cases, throughput may be reduced by utilizing the fact that insuch APs the transmitter can transmit via several RF chains. Thisfacilitates transmission in parallel on several single channels. It canshorten the scan by the number of frequencies (2 or 3 or 4).Unfortunately, this approach may require the receiver to support themultiple frequencies scan, and it is not backward compatible (e.g., with802.11ad devices) and requires the stations to fully be aware of thisspecial mode in advance. In some cases, the Tx SLS+Rx SLS or the TxSLS+Rx BRP may be replaced with a new Tx+Rx BRP where only one “very”long BRP message is used with many TRN units. Unfortunately, this methodrequires a very long message but may be able to support multiple STAs inparallel, making it efficient but only in cases with a large number ofSTAs.

Example Double One-Dimensional Sector Sweep Scan

Aspects of the present disclosure provide techniques that may allow foran enhanced sector sweep that utilizes two or more one-dimensionalsector sweep scans. As noted above, a conventional sector sweep may taketoo long for wireless devices with hundreds of pencil beam sectors(e.g., 256, 512, or 1024). Certain aspects presented herein, address thesweep duration by sweeping a coverage area using wide one-dimensionalsectors. For example, suppose an AP has N sectors formed by an antennaarray having K×L antenna elements (where N=K×L). A pencil beam scan aspreviously described requires N messages to be sent, each in a differentdirection. The sector sweep of the present disclosure may be performedfor each row and column of the antenna array, yielding a sector sweephaving (K+L) one-dimensional sectors, reducing the scanning timesignificantly. In some instances, the sector sweep may be reduced by afactor of 16, for example, where N=1024, K=32, and L=32. Such a sectorsweep may be used for improving beamforming training and/or devicepositioning applications (e.g., passive positioning) as furtherdescribed herein.

FIG. 6 illustrates example operations 600 for performing one-dimensionalsector sweeps, in accordance with certain aspects of the presentdisclosure. The operations 600 may be performed, for example, by an AP(e.g, AP 110) or a STA (e.g., user terminal 120). Operations 600 may beimplemented as software components that are executed and run on one ormore processors (e.g., controller 230 of FIG. 2). In certain aspects,the transmission and/or reception of signals by the AP may beimplemented via a bus interface of one or more processors (e.g.,controller 230) that obtains and/or outputs signals. Further, thetransmission and reception of signals by the AP of operations 600 may beenabled, for example, by one or more antennas and/ortransmitter/receiver unit(s) (e.g., antenna(s) 224 ortransmitter/receiver unit(s) 222 of FIG. 2).

The operations 600 begin, at 602, by the AP or STA (also referred toherein as a “sweep initiator”) generating a first set of frames and asecond set of frames. At 604, the AP or STA outputs the first set offrames for transmission to a wireless node (e.g., user terminal 120 oranother AP, also referred to herein as a “sweep receiver”) via a firstset of beams, wherein each beam of the first set is wider in a firstdimension than a second dimension. At 606, the AP or STA outputs thesecond set of frames for transmission to the wireless node via a secondset of beams, wherein each beam of the second set is wider in the seconddimension than the first dimension.

The sweep receiver may use the received one-dimensional sector sweepframes to determine an angle of departure (AoD) of the frames and/or alocation of the sweep receiver as further described herein. For example,FIG. 7 illustrates example operations 700 for receiving theone-dimensional sector sweep frames, in accordance with certain aspectsof the present disclosure. The operations 700 may be performed, forexample, by a STA (e.g., user terminal 120) or an AP (e.g., AP 110).Operations 700 may be implemented as software components that areexecuted and run on one or more processors (e.g., controller 280 of FIG.2). In certain aspects, the transmission and/or reception of signals bythe STA may be implemented via a bus interface of one or more processors(e.g., controller 280) that obtains and/or outputs signals. Further, thetransmission and reception of signals by the STA of operations 700 maybe enabled, for example, by one or more antennas and/ortransmitter/receiver unit(s) (e.g., antenna(s) 252 ortransmitter/receiver unit(s) 254 of FIG. 2).

The operations 700 begin, at 702, by the AP or STA (also referred toherein as a “sweep receiver”) obtaining, from a wireless node (e.g., thesweep initiator of operations 600), a first set of frames transmittedvia a first set of beams, wherein each beam of the first set is wider ina first dimension than a second dimension. At 704, the AP or STA, fromthe wireless node, obtains a second set of frames transmitted via asecond set of beams, wherein each beam of the second set is wider in thesecond dimension than the first dimension. At 706, the AP or STAdetermines reception parameters for the first and second sets of frames.At 708, the AP or STA determines at least one of an angle of departureof the first and second sets of frames, a location of the apparatusrelative to the wireless node, or an absolute location of the apparatusbased on the reception parameters. At 710, the AP or STA may,optionally, take one or more actions based on at least one of the angleof departure of the first and second set of frames, the location of theSTA relative to the wireless node, or the absolute location of the STA.

As noted above, during the one-dimensional sweep, a first set ofone-dimensional sector sweep (SSW) frames is transmitted via beams thathave a wider first dimension than a second dimension. In certainaspects, this first set of beams may correspond to different elevationdirections (or angles). For example, FIG. 8 illustrates an exampleradiation pattern of one-dimensional elevation beams 802, in accordancewith certain aspects of the present disclosure. The elevation beams 802are depicted in a coordinate system having an x-axis 806, y-axis 808,and z-axis 810. Each elevation beam 804 has a beam pattern that is widerin the azimuthal dimension than the elevation dimension. In other words,each elevation beam 804 has a wider equatorial dimension than thedimension of its poles. Each elevation beam 804 may dip at a differentangle relative to a reference plane (e.g., a horizontal plane that runsparallel to the x-axis 806 and the y-axis 808) or relative to anotherelevation beam. Each beam of the elevation beams 802 may correspond to adifferent transmit direction along the first dimension that isassociated with a different angle in the narrower elevation dimension(e.g., the set of beams transmitted at 604).

As noted above, a second set of frames are transmitted via beams thathave a wider second dimension than the first dimension. In certainaspects, this second set of beams may correspond to different azimuthaldirections. For example, FIG. 9 illustrates an example radiation patternof one-dimensional azimuthal beams 902, in accordance with certainaspects of the present disclosure. The azimuthal beams 902 are depictedin the three-dimensional coordinate system (x-axis 806, y-axis 808, andz-axis 810). Each azimuthal beam 904 has a beam pattern that is wider inthe elevational dimension than the azimuthal dimension. In other words,the azimuthal beam 904 has a wider dimension at its poles than theequatorial dimension. Each azimuthal beam 904 may be spaced at adifferent azimuthal direction relative to a reference plane (e.g., avertical plane that runs parallel to the y-axis 808 and the z-axis 810)or relative to another azimuthal beam. Each beam of the azimuthal beams902 may correspond to a different transmit direction along the firstdimension that is associated with a different angle in the narrowerazimuthal dimension (e.g., the set of beams transmitted at 606).

In certain aspects, the first set of beams collectively spansapproximately a same coverage area as the second set of beams. Forexample, the elevation beams 802 spans approximately the same coveragearea as the azimuthal beams 902. As shown, the elevation beams 802 areorthogonal to the azimuthal beams 902. In certain aspects, the elevationbeams and the azimuthal beams may not be orthogonal to each other. Forexample, the elevation beams 802 may be tilted relative to the y-axis808. In another example, the azimuthal beams 902 may be tilted relativeto the z-axis 810. In certain aspects, the first set of beams (e.g., theset of beams transmitted at 604) may include elevation and/or azimuthalbeams. Similarly, the second set of beams (e.g., the set of beamstransmitted at 606) may include elevation and/or azimuthal beams.

In certain aspects, the sweep initiator may initially provide the sweepreceiver with directional information related to each one-dimensionalsector used in the one-dimensional sector sweeps. For example, the sweepinitiator may transmit to the sweep receiver a frame includinginformation indicative of angular directions (e.g., angles of departure)for sets of beams (e.g., the elevation beams 802 and the azimuthal beams902) used during the one-dimensional sector sweep. That is, the sweepreceiver may obtain at least one frame with information regarding thedirectional mapping of the beam indexes in the first set of frames andthe directional mapping of the beam indexes in the second set of frames.In certain aspects, the sweep receiver may initially obtain thedirectional information via a common database or common server on theweb. For example, the sweep receiver may obtain the directionalinformation from a server or another wireless node (e.g., an AP or STAdifferent from the sweep initiator) that collects the directionalinformation for multiple APs.

In certain aspects, the angular directions may be relative to a commoncoordinate reference system (such as a latitude, longitude, and/orelevation). The directional information may correspond to indices thatidentify the one-dimensional sectors of the sweep initiator. That is,the directional information may be a data structure including indicesthat map to angular directions. The directional information may alsoindicate the coordinate reference system of the angular directions. Incertain aspects, the directional information may be included in locationconfiguration information (LCI) message. The directional information mayalso indicate to the sweep receiver that the sweep initiator is capableof performing a one-dimensional sector sweep as described herein.

In certain aspects, each of the one-dimensional sector sweep frames mayinclude a beam index indicating which one-dimensional beam was used tooutput the sector sweep frame for transmission. That is, each frame ofthe first and second sets has a beam index indicating a beam via whichthe frame was output for transmission. For example, each beam index inthe first set of frames may map to an angle of departure from the sweepinitiator in the second dimension, whereas each beam index in the secondset of frames may map to an angle of departure from the sweep initiatorin the first dimension. The sweep receiver may use this beam index todetermine the angular direction from which the frame was sent by thesweep initiator based on the previously received directionalinformation. In other words, the sweep receiver may determine the angleof departure (AoD) of each one-dimensional sector sweep frame receivedbased on a combination of the beam index of at least one of the firstset of frames and the beam index of at least one the second set offrames. For example, the sweep receiver may determine the AoD of eachsweep sector frame based on the beam indices and the previously receiveddirectional information corresponding to the beam indices.

The sweep receiver may also determine the angle of departure (AoD) basedon at least one of: an interpolation between two of the angles in thesecond dimension or an interpolation between two of the angles in thefirst dimension. For example, the sweep receiver may interpolate theangle of departure for the azimuthal direction between the two strongestreceived signals from the azimuthal beams 902. The sweep receiver mayperform a similar interpolation to estimate the angle of departure forthe elevation direction between the two strongest received signals fromthe elevation beams 802.

In certain aspects, each frame of the first and second sets includes anidentification of the sweep initiator. For example, each frame of thefirst and second sets may have an index identifying the sweep initiator.The sweep receiver may determine an absolute location of the sweepinitiator based on this identification and the AoD of the sweep frames.

In certain aspects, the sweep receiver may provide feedback to the sweepinitiator. The feedback may include information generated based onreception parameters determined by the sweep receiver (e.g., at 706) forthe first and second sets of one-dimensional sector sweep frames. Incertain aspects, the feedback information generated may be an indicationof the received signal strength of the one-dimensional sectors receivedby the sweep receiver. That is, the reception parameters may include anindication of the received signal strengths for the received sectorsweep frames.

For example, the sweep receiver may generate a feedback frame includinginformation regarding the reception parameters determined at 706. Thesweep receiver outputs the feedback frame for transmission to the sweepinitiator. The sweep receiver obtains from the sweep initiator, aresponse frame. The sweep initiator determines the AoD of the framesbased on information included in the response frame. This may enable thesweep receiver to offload the determination to the sweep initiator oranother device.

The sweep initiator may determine, based on the received feedbackinformation, at least one of an angle of departure of the first andsecond one-dimensional sector sweep frames at the sweep receiver, alocation of the sweep receiver relative to the sweep initiator, or anabsolute location of the sweep receiver. For example, the sweepinitiator may determine the AoD based on the indications of the receivedsignal strengths at the sweep receiver corresponding to theone-dimensional sectors. The sweep initiator may use the AoD forconfiguring its antenna elements to directionally transmit signals tothe sweep receiver.

As noted above, the sweep receiver may take one or more actions based onvarious parameters (e.g., the angle of departure of the first and secondsets of frames, the location of the sweep receiver relative to the sweepinitiator, or the absolute location of the sweep receiver) determined bythe sweep receiver. In certain aspects, the one or more actions mayinclude changing an antenna configuration of the sweep receiver. Forinstance, the sweep receiver may configure its receive antenna elementsfor directional reception based on an angle of departure. The one ormore actions may also include using, for example, the angle of departureof the first and second sets of frames, the relative location of thesweep receiver relative to the sweep initiator, or the absolute locationof the sweep receiver for location based services such as a navigationservice. The one or more actions may include reporting, for example, thelocation of the sweep receiver relative to the sweep initiator or theabsolute location of the sweep receiver to a higher layer application(such as a navigation application) or another device (such as a servermonitoring the location of the sweep receiver).

Aspects of the present disclosure provide techniques where a station mayperform positioning (e.g., passive positioning) based on a departuredirection, which may be represented as an angle of departure (AoD), ofthe one-dimensional sector sweep frames.

As illustrated in FIG. 10, using the AoDs from two different APs thedifference angle of pointing vectors to these APs can be found. Asillustrated in FIG. 10, this defines a section of a circle (in 3dimensions, a sphere). In two dimension, if the AP sits at points (inthe x,y plain—(−d/2,0), (d/2), the circle can be parametrically definedas

${x = {{\frac{D}{\sin(\theta)}\;\sin\;\left( {\alpha + \theta} \right)\;\cos\;(\alpha)} - \frac{D}{2}}},{y = {\frac{D}{\sin\;(\theta)}\;\sin\;\left( {\alpha + \theta} \right)}},$where θ is the angle between directions and 0<α<π−θ is a runningparameter. FIG. 10 shows how circles are formed from specific angles andthe base lines which are the lines connecting the APs. The (2-D)position of the STA (within a plane) may be found as an intersection ofthe two circles (e.g., given the equations as defined above). As theintersection is at two points, information from the third AP may be usedto resolve which of the two intersecting points to use for the positionestimate. In this manner, 3 APs may allow estimation of location in aplane, while 4 APs allow location estimation in 3 dimensions. Similarly,4 APs may allow the (3-D) position of the STA to be found as anintersection of three (or four) spheres (e.g., given correspondingparametrically defined equations).

Techniques described herein provide various advantages to scanningsectors, in particular, for mmWave applications with transmitters havinghundreds of antenna elements. For example, the one-dimensional sectorsweep described herein may enable transmitters to significantly reduce asector sweep duration, which may also improve beamforming training andpositioning applications.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. All structural andfunctional equivalents to the elements of the various aspects describedthroughout this disclosure that are known or later come to be known tothose of ordinary skill in the art are expressly incorporated herein byreference and are intended to be encompassed by the claims. Moreover,nothing disclosed herein is intended to be dedicated to the publicregardless of whether such disclosure is explicitly recited in theclaims. No claim element is to be construed under the provisions of 35U.S.C. § 112, sixth paragraph, unless the element is expressly recitedusing the phrase “means for” or, in the case of a method claim, theelement is recited using the phrase “step for.”

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software component(s)and/or module(s), including, but not limited to a circuit, anapplication specific integrated circuit (ASIC), or processor. Generally,where there are operations illustrated in figures, those operations mayhave corresponding counterpart means-plus-function components withsimilar numbering. For example, operations 600 and 700 illustrated inFIGS. 6 and 7 correspond to means 600A and 700A illustrated in FIGS. 6Aand 7A.

Means for receiving, means for taking one or more actions, means forchanging an antenna configuration, or means for obtaining may comprise areceiver (e.g., the receiver unit 222) and/or an antenna(s) 224 of theaccess point 110 or the receiver unit 254 and/or antenna(s) 252 of theuser terminal 120 illustrated in FIG. 2. Means for transmitting, meansfor taking one or more actions, means for reporting, means for changingan antenna configuration, or means for outputting may comprise atransmitter (e.g., the transmitter unit 222) and/or an antenna(s) 224 ofthe access point 110 or the transmitter unit 254 and/or antenna(s) 252of the user terminal 120 illustrated in FIG. 2. Means for generating,means for determining, means for logging, means for taking one or moreactions, means for reporting, means for changing an antennaconfiguration, means for outputting, or means for obtaining may comprisea processing system, which may include one or more processors, such asthe RX data processor 242, the TX data processor 210, the TX spatialprocessor 220, RX spatial processor 240, and/or the controller 230 ofthe access point 110 or the RX data processor 270, the TX data processor288, the TX spatial processor 290, RX spatial processor 260, and/or thecontroller 280 of the user terminal 120 illustrated in FIG. 2.

In some cases, rather than actually transmitting a frame a device mayhave an interface to output a frame for transmission (a means foroutputting). For example, a processor may output a frame, via a businterface, to a radio frequency (RF) front end for transmission.Similarly, rather than actually receiving a frame, a device may have aninterface to obtain a frame received from another device (a means forobtaining). For example, a processor may obtain (or receive) a frame,via a bus interface, from an RF front end for reception.

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “determining” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” may include resolving, selecting, choosing, establishingand the like.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover a, b, c,a-b, a-c, b-c, and a-b-c, as well as combinations that include multiplesof one or more members (aa, bb, and/or cc).

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device (PLD),discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thepresent disclosure may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Asoftware module may reside in any form of storage medium that is knownin the art. Some examples of storage media that may be used includerandom access memory (RAM), read only memory (ROM), flash memory, EPROMmemory, EEPROM memory, registers, a hard disk, a removable disk, aCD-ROM and so forth. A software module may comprise a singleinstruction, or many instructions, and may be distributed over severaldifferent code segments, among different programs, and across multiplestorage media. A storage medium may be coupled to a processor such thatthe processor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor.

The methods disclosed herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

The functions described may be implemented in hardware, software,firmware, or any combination thereof. If implemented in hardware, anexample hardware configuration may comprise a processing system in awireless node. The processing system may be implemented with a busarchitecture. The bus may include any number of interconnecting busesand bridges depending on the specific application of the processingsystem and the overall design constraints. The bus may link togethervarious circuits including a processor, machine-readable media, and abus interface. The bus interface may be used to connect a networkadapter, among other things, to the processing system via the bus. Thenetwork adapter may be used to implement the signal processing functionsof the PHY layer. In the case of a user terminal 120 (see FIG. 1), auser interface (e.g., keypad, display, mouse, joystick, etc.) may alsobe connected to the bus. The bus may also link various other circuitssuch as timing sources, peripherals, voltage regulators, powermanagement circuits, and the like, which are well known in the art, andtherefore, will not be described any further.

The processor may be responsible for managing the bus and generalprocessing, including the execution of software stored on themachine-readable media. The processor may be implemented with one ormore general-purpose and/or special-purpose processors. Examples includemicroprocessors, microcontrollers, DSP processors, and other circuitrythat can execute software. Software shall be construed broadly to meaninstructions, data, or any combination thereof, whether referred to assoftware, firmware, middleware, microcode, hardware descriptionlanguage, or otherwise. Machine-readable media may include, by way ofexample, RAM (Random Access Memory), flash memory, ROM (Read OnlyMemory), PROM (Programmable Read-Only Memory), EPROM (ErasableProgrammable Read-Only Memory), EEPROM (Electrically ErasableProgrammable Read-Only Memory), registers, magnetic disks, opticaldisks, hard drives, or any other suitable storage medium, or anycombination thereof. The machine-readable media may be embodied in acomputer-program product. The computer-program product may comprisepackaging materials.

In a hardware implementation, the machine-readable media may be part ofthe processing system separate from the processor. However, as thoseskilled in the art will readily appreciate, the machine-readable media,or any portion thereof, may be external to the processing system. By wayof example, the machine-readable media may include a transmission line,a carrier wave modulated by data, and/or a computer product separatefrom the wireless node, all which may be accessed by the processorthrough the bus interface. Alternatively, or in addition, themachine-readable media, or any portion thereof, may be integrated intothe processor, such as the case may be with cache and/or generalregister files.

The processing system may be configured as a general-purpose processingsystem with one or more microprocessors providing the processorfunctionality and external memory providing at least a portion of themachine-readable media, all linked together with other supportingcircuitry through an external bus architecture. Alternatively, theprocessing system may be implemented with an ASIC (Application SpecificIntegrated Circuit) with the processor, the bus interface, the userinterface in the case of an access terminal), supporting circuitry, andat least a portion of the machine-readable media integrated into asingle chip, or with one or more FPGAs (Field Programmable Gate Arrays),PLDs (Programmable Logic Devices), controllers, state machines, gatedlogic, discrete hardware components, or any other suitable circuitry, orany combination of circuits that can perform the various functionalitydescribed throughout this disclosure. Those skilled in the art willrecognize how best to implement the described functionality for theprocessing system depending on the particular application and theoverall design constraints imposed on the overall system.

The machine-readable media may comprise a number of software modules.The software modules include instructions that, when executed by theprocessor, cause the processing system to perform various functions. Thesoftware modules may include a transmission module and a receivingmodule. Each software module may reside in a single storage device or bedistributed across multiple storage devices. By way of example, asoftware module may be loaded into RAM from a hard drive when atriggering event occurs. During execution of the software module, theprocessor may load some of the instructions into cache to increaseaccess speed. One or more cache lines may then be loaded into a generalregister file for execution by the processor. When referring to thefunctionality of a software module below, it will be understood thatsuch functionality is implemented by the processor when executinginstructions from that software module.

If implemented in software, the functions may be stored or transmittedover as one or more instructions or code on a computer-readable medium.Computer-readable media include both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage medium may be anyavailable medium that can be accessed by a computer. By way of example,and not limitation, such computer-readable media can comprise RAM, ROM,EEPROM, CD-ROM or other optical disk storage, magnetic disk storage orother magnetic storage devices, or any other medium that can be used tocarry or store desired program code in the form of instructions or datastructures and that can be accessed by a computer. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared (IR),radio, and microwave, then the coaxial cable, fiber optic cable, twistedpair, DSL, or wireless technologies such as infrared, radio, andmicrowave are included in the definition of medium. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Thus, in some aspects computer-readable media maycomprise non-transitory computer-readable media (e.g., tangible media).In addition, for other aspects computer-readable media may comprisetransitory computer-readable media (e.g., a signal). Combinations of theabove should also be included within the scope of computer-readablemedia.

Thus, certain aspects may comprise a computer program product forperforming the operations presented herein. For example, such a computerprogram product may comprise a computer-readable medium havinginstructions stored (and/or encoded) thereon, the instructions beingexecutable by one or more processors to perform the operations describedherein. For certain aspects, the computer program product may includepackaging material.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a user terminal and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a userterminal and/or base station can obtain the various methods uponcoupling or providing the storage means to the device. Moreover, anyother suitable technique for providing the methods and techniquesdescribed herein to a device can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

What is claimed is:
 1. An apparatus for wireless communication,comprising: a processing system configured to generate a first set offrames and a second set of frames; and a first interface configured to:output the first set of frames for transmission to a wireless node via afirst set of beams, wherein each beam of the first set is wider in afirst dimension than a second dimension, wherein the first dimensioncorresponds to elevation and the second dimension corresponds toazimuth, and wherein each beam of the first set corresponds to adifferent transmit direction along the first dimension that isassociated with a different angle in the second dimension, and outputthe second set of frames for transmission to the wireless node via asecond set of beams, wherein each beam of the second set is wider in thesecond dimension than the first dimension, and wherein each beam of thesecond set corresponds to a different transmit direction along thesecond dimension that is associated with a different angle in the firstdimension, wherein the first set of beams collectively spansapproximately a same coverage area as the second set of beams.
 2. Theapparatus of claim 1, wherein each frame of the first and second setshas a beam index indicating a beam via which the frame was output fortransmission.
 3. The apparatus of claim 1, further comprising a secondinterface, wherein: the second interface is configured to obtain afeedback frame from the wireless node including information generatedbased on reception parameters determined by the wireless node for thefirst and second sets of frames; and the processing system is configuredto determine, based on the information, at least one of an angle ofdeparture of the first and second sets of frames at the wireless node, alocation of the wireless node relative to the apparatus, or an absolutelocation of the wireless node.
 4. The apparatus of claim 3, wherein theprocessing system is further configured to at least one of: change anantenna configuration based on at least one of the angle of departure ofthe first and second sets of frames, the location of the wireless noderelative to the apparatus, or the absolute location of the wirelessnode; or report at least one of the location of the wireless noderelative to the apparatus or the absolute location of the wireless node.5. The apparatus of claim 1, wherein: the processing system isconfigured to generate at least one frame including informationindicative of angular directions of the first set of beams and thesecond set of beams; and the first interface is configured to output theat least one frame for transmission.
 6. A method for wirelesscommunication by an apparatus, comprising: generating a first set offrames and a second set of frames; outputting the first set of framesfor transmission to a wireless node via a first set of beams, whereineach beam of the first set is wider in a first dimension than a seconddimension, wherein the first dimension corresponds to elevation and thesecond dimension corresponds to azimuth, and wherein each beam of thefirst set corresponds to a different transmit direction along the firstdimension that is associated with a different angle in the seconddimension; and outputting the second set of frames for transmission tothe wireless node via a second set of beams, wherein each beam of thesecond set is wider in the second dimension than the first dimension,and wherein each beam of the second set corresponds to a differenttransmit direction along the second dimension that is associated with adifferent angle in the first dimension, wherein the first set of beamscollectively spans approximately a same coverage area as the second setof beams.
 7. The method of claim 6, wherein each frame of the first andsecond sets has a beam index indicating a beam via which the frame wasoutput for transmission.
 8. The method of claim 6, further comprising:obtaining a feedback frame from the wireless node including informationgenerated based on reception parameters determined by the wireless nodefor the first and second sets of frames; and determining, based on theinformation, at least one of an angle of departure of the first andsecond sets of frames at the wireless node, a location of the wirelessnode relative to the apparatus, or an absolute location of the wirelessnode.
 9. The method of claim 8, further comprising at least one of:changing an antenna configuration based on at least one of the angle ofdeparture of the first and second sets of frames, the location of thewireless node relative to the apparatus, or the absolute location of thewireless node; or reporting at least one of the location of the wirelessnode relative to the apparatus or the absolute location of the wirelessnode.
 10. The method of claim 6, further comprising: generating at leastone frame including information indicative of angular directions of thefirst set of beams and the second set of beams; and outputting the atleast one frame for transmission.